Pulp grinding stone



March 22,1932

- W. W. GREENWOOD PULP GRINDING STONE Filed Aug. 6, 1924 wglface 68.3..

W. Grenwbod Patented Mar. 22, 1932 UNITED STATES- PATENT OFFICE W. GREENWOOD, OF WORCESTER, llASSAQEUSETTS, ASSIGNOR TO NORTON COMPANY, OF WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS run camnme sronn' Application filed August 8, 1924. Serial No. 780,517.

This invention relates to abrasive wheels and more particularly to a segmental grinding wheel of artificial abrasive bonded with ceramic material which is particularly adapted for grindin wood pulp.

In the manu acture of paper from wood it has heretofore been customary to grind logs by means of natural sandstones or with inding wheels composed of abrasive grains bonded with some cold set cement. The cement bonded stones are ordinarily used only in a cold grinding process, whereas the preferred process in this country involves grinding with but little cooling water and utilizing the frictional heat to loosen the bondsbetween the pulp fibres. A temperature as high as 160 to 180 F. is desirable,

but heretofore the artificially bonded wheels tried for this purpose have been detrimentally affected by the combination of heat and water.

In order that sandstones may be used eflicient- 1y for making long fibre pulp, it has been found necessary to provide high ridges on its cutting face, which is known to the trade as burring the stone. This procedure is Wasteful of the expensive stone and consumes valuable time which should be devoted'to frequent intervals; hence the stone is short lived.

Various efforts have been made to employ a grinding wheel of the type used in the metal industries but heretofore this has not proven successful. A stone as large as is normally required for grinding' wood pulp efiiciently is diflicult to manufacture, and the firing of such a large piece in commercial kilns is likely to produce a wheel not properly annealed and therefore susceptible of breakage during use. It is therefore desirable to make the wheel of-separately fashioned abrasive segments mounted on a rotatable support. and particularly to mount them on the cylindrical surface of a drum and secure them rigidly in position by adjustable clamping devices. Due, however, to the fact that abrasive segments are ordinarily rough surfaced and crudely shaped, it is not easy to clamp, the

exposed so that they wear ofl or break away,

thus enlarging the space between the segments and detrimentally affecting the grinding operation.

It is one object of this invention to overcome such difliculties and to provide a satisfactory pulp grinding stone made of segments of bonded artificial abrasive mounted on a rotatable support, which will beefficient and long lived in its service.

A further object is to so construct such a wheel that the segments will be mounted accurately and held securely against the stresses ofthe grinding operation, and particularly to insure that the forces involved in fastening the segments in position will be widely distributed through the abrasive body and thereby minimize the danger of breakage of the wheel. r

A still further object is to provide a segmental wheel of artificial abrasive in which the segments will be protected from uneven wear and breakage at their adjacent edges and they will be supported laterally and held rigidly in position.

' With these and other objects in view as will be apparent to one skilled in the art, my invention consists of the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawings which illustrate one embodiment of my invention:

Fig. 1 is an end view of a wood pulp grinding stone ready for mounting on its grinding spindle;

'2 is a front elevation of the .stone mounted on the spindle and showing the arrangement of the segments;

Fig. 3 is a diametrical section through the stone; and

of bond and 85 to 82 parts of Various Well known ceramic practices may Fig. 4 is an enlarged fragmentary detail in cross section showing the manner of mounting the segments.

In accordance with my invention I propose to make pulp grinding stones of the modern artificial abrasives which have a hardness of 9 or more on Mohs scale, such as crystalline alumina and silicon carbide, and to bond them with suitable bonds, such as vitrified ceramic materials. These stones are formed as segments of suitable shape adapted to be mounted on a rotatable drum. In order that the segments may be accurately mounted in position I propose to form them with carefully shaped surfaces which will fit against the periphery of the drum and against the clampin devices employed to hold them in place. ince these blocks are necessarily separated by crevices it is important that provision be made to prevent splinters of wood from coming through unground and to protect the corners of the segments. Hence I propose to fill the cracks with a material which has such characteristics that it will wear away at substantially the same rate as that at which the abrasive stone decreases in size, and to this end I prefer to employ a tough, ductile, non-brittle, insoluble substance. which may be poured into the crevices and will there harden in lace.

Abrasive elements suitable for grinding pulp for news print paper may be made in accordance with usual grinding wheel practice by utilizing silicon carbide granules of such a grit size that the major portion of them will just pass through a screen of 24 meshes to the linear inch, although wide variations from this grit size may be made. These grains are bonded with a ceramic bond which is capable of being vitrified under the usual ceramic kiln treatment. For this purpose I may employ a suitable bond mixture and so proportion the ingredients that a stone of an open porous structure is obtained. As an example of one type of bond composition. which I may use, the following may be employed in the proportions specified Per cent by wei ht Feldspar 50 to 0 Ball clay 10 to 30 Ground quartz 15 to 25 This bond may be mixed with silicon carbide abrasive grains of about 24 grit size in the proportion of 15 to 18 parts by weight abrasive.

be employed in making the stone, which comprise mixing the abrasive and bond materials with water to form a suitable mouldable or plastic mass, shaping a Wheel segment therefrom, drying the shape and then firingit in a ceramic kiln at a temperature approximatin Orton cone v12 which causes the ceramic bond to vitrify and unite the abrasive means of threaded wil grains together into a porous integral mass.

Referring to the drawings which illustrate one suitable shape of segment and a simple means of mounting the segments on a drum, I have there shown a driven spindle 10 to which is keyed the hub 11 of the drum 12, supported on a central web 13 and radial flanges 14. This drum 12 has an outer cylindrical surface 15, which is shaped fairly accurately. The segments 16 are so shaped that when mounted on the drum they fit against surface 15 and form an outer cylindrical abrasive surface. In order to make a wide wheel, it is preferable to employ more than one row of segmental blocks on the cylinder. and these may be shaped as illustrated to form staggered joint lines 17 which will mini mize the tendency for slivers to be carried past in the crevices between the rows of segments.

One manner of fastening the segments on the drum involves providing each segment with an inner dove-tailed portion 18 arranged to be held in place by interfitting parts carried on the drum. A simple form of clamp comprises wedge blocks 20 arranged in the grooves 21 between the dove-tailed portions of the segments. These blocks 20 are adapted tobe fastened to the drum 12 by studs 22, which pass through the drum and are secured thereto by nuts 23 on their inner ends. The outer end of each stud 22 is screw-threaded into the wedge block 20, so that the block may be drawn down to a given position and then fixed in place. Any other suitable means may be employed for fastening the blocks in place. The specific structure of the alternately arrange clamping and locating blocks is claimed in the copending patent to Larsson No. 1,684,770.'

In order that the abrasive segments may make full and proper contact with the cy- .lindrical surface of the drum and with the wedge faces of the clamping blocks, I provide each se ment 16 with a smooth facing or shoe 28, w ich has been shaped in a mould or otherwise to fit accurately against the drum and wedge faces. This shoe is preferabl made of a soft metal, such as lead, which l flow easily into the surface pores of the stone and thereby fasten the shoe firmly in position. A soft metal moreover will provide a safer support for the segment and flow sufiiciently as required by any unevenness in the drum surface to position the block correctly. It 'will therefore be seen that the segments may be accurately positioned in accordance with the shape of the metal faces, and that the wedge blocks merely serve to clamp fitted surface portions securely in place and do not cause any strain which would break the segments. If desired, the metal faces need not extend throughout the full width of the under surface, so as to leave a The segments are provided with an inner surslight space 29 for the metal to flow under the pressure of clam ing.

After the bloc s have been put in place I then fill the-cracks between the blocks with a composition capable of resisting abrasion under the pressure 'of the logs a nst "the wheel and of wearing away at su stantially the same rate as the segments. I prefer to employ a substance which may be poured into the crevices and will fill the surface pores of the segments and there harden in lace. It is also desirable that this material re-i sistant to the action of heat and water, as met in the normal grinding operation, and that it be non-brittle, tough and ductile, but not so soft that it will smear over the face of the stone during grinding. I prefer to use a.

low melting metal which may be heated and which will not affect the wheel detrimentally. One suitable filler is a Babbitt metal which has substantially the same wearing capacity as the stoneduring the grinding operation Per cent by weight Tin 91 Antimony 4.5

Copper 4.5

An alloy of this composition has a Brinell hardness at 212 F. of 12.8 and a melting point of 437 F. I

It is found feasible to use this same composition for the shoe or lining 28 as well, and I prefer to so shape the parts that the alloy will run down the crevices between the segments and fill completely the space 30 left between the segment and the wedge block thereby insuring a solid foundation for the segments and preventing their working loose on the drum.

In accordance with this invention, I have provided an artificial pulp stone which will grind pulp and produce long fibres and which will have a long and eflicient life and not be detrimentally affected by heat and water.

face layer of metal integral therewith which prevents breakage of the segment under normal usage and the filler between the segments minimizes to the formation of unground slivers of wood. The stone requires the minimum of attention and dressing and it is not necessary. to cut deep grooves on the face of the stone with a consequent loss of abrasive material. Moreover if by an accident one of ters Patent is the segments should become cracked or broken it may be easily removed without interferin be noted that the fillin metal between the with the remainder of the wheel and rep aced by a new segment. It will also segments supports the ater on their sides and makes a solid and unitary ring of the abrasive material, and the metal shoes insure a firm mounting for the rin which will prevent all movement between 1ts parts'and the clamping members. It will also'be apparent that this invention is not limited m its broader aspects to a particular shape of stone, and the term segment as herein employed is intended to cover disk sections or other small shapes which may be mounted on a-rotatablespindle to form a large pulp "stone. poured into the crevices at a temperature Having thus described my invention, what I claim as new and desire to secure 1. A grinding wheel comprising abrasive segments of bonded anular material, suitable for hot, wet grin ing of pulp wood which are arranged to form a grinding surface, means for rotatably supporting the segments, and a metal filler in the crevices between and adjacent'to the exposed ed es of the segby Let-.

ments which is composed o a material capable of conforming to the surfaces of the segments but is of such a nature that, while it will wear away under a normal grinding operation at substantially thesame rate as that at which the segments wear so that the crevices will remain filled to the operative surface of the wheel, it also resists abrasion effectively during grinding and has sufiicient inherent rigidity to transmit peripheral stress from one segment to another without crushin so as to support and protect the edges of the segments. 1

2. A grinding wheel comprising a rotatable member, a plurality of segments of ceremic bonded abrasive grains mounted thereon to form an abrading surface, adjustable devices for fastening the se ments firmly on said member, and a tough, urable metal filling. material in the crevices between the segments which makes close contact therewith and has suflicient inherent rigidity to transmit any lateral thrust upon one segment to a neighboring segment and which is capable of wearing away with the segments and of supporting their adjacent faces so as to protect their corners during the normal usage of the wheel.

3. A grinding wheel comprising a rotat able member, a row of ceramic bonded abrasive segments mounted on said member in spaced relation and arranged to form an operative grinding surface, and a metal filler in the crevices between and contacting firmly with the segments which is capable of supporting them laterally under the stresses of the normal grinding operation and protecting the ed es of the segments frombreaking.

4. A u p grinding stone comprising a rotatable rum, a lurality of segmentsn dly mounted on sai drum and a filler of ab- 5 bitt metal in the crevices between the segments which will maintain the crevices filled to substantiall the c lindrical surface of the grinding w eel an protect the edges of the segments during the normal grinding 110 operation. I p

5. A grinding wheel comprising a rotatable support, porous segments of bonded abrasive grains suitable for hot, wet mdmg of wood pulp mounted and fastene thereon 1n spaced relationship and a filler of a low melting, ductileand durable metal.flowed into the crevices between the segments and into their surface pores and thereby uniting the segments into an integral abrading ring.

6. A grinding wheel comprising a rotatable drum, a plurality of segments of bonded abrasive grains mounted thereon and arranged to form an annular grinding wheel, '25 adjustable devices to fasten the segments firmly in position, and a filler of a low melting ductile metal flowed into the crevice between adjacent segments and uniting the segments into an integral abrading body.

7. A grinding wheel com rising a rotatable cylindrical sup ort havlng a peripheral surface on which a rasive segments are to be mounted, abrasive se ents supported solely on said surface anf f orming a cylindrical grinding surface, a shoe between each segment and the rotatable support which fits the segment and said peripheral" surface and thereby positions the segment correctly, and adjustable devices clamping against the segments which serve to fasten them ri 'dly in place with the shoes held tightly against the rotatable support. Y

8. A grinding wheel comprising a rotatable drum having a peripheral surface, a plurality of ceramic bonded abrasive segments arranged thereon to form a grindin surface, each segment having an inner acing of metal integral therewith which has a surface fitting against said peripheral surface, 50 and a clampin device arranged to secure the segment rigidly in position on the drum.

9. A grinding wheel comprisin a rotatable support having a surface on w ich abrasive segments are to be mounted, abrasive segments arranged thereon to form a grinding surface and provided with clamping shoulders, shoes contacting intimatel with the inner faces of the segments whic have faces fitting against said surface of the rotatable support and serve to transmit stresses in the segments to the support throughout an extensive area, and adjustable devices cooperating with the support and clamping against said shoulders to fasten the segments tightly in position.

10. A grinding wheel comprisin a rotatably mounted drum having a cylin rical surface, a lurality of. porous segments of ceramic onded abrasive ains mounted solely on said surface and orming a cylindrical grinding surface, each segment having a facing shoe united intimately with its in nor porous surface which fits accurately against the cylindrical surface of the drum and thereby positions the segment correctly, and adjustable members on the drum to fasten the segments with their shoes rigidly in contact with said drum surface.

11. A grinding wheel comprising a rotatable support having a cylindrical surface, a plurality of abrasive segments mounted on said surface and forming a cylindrical grinding surface, and a clamping member associated with said rotatable support for adjustably and removably fastening the segments thereon, each segment having a facing formed integrally therewith which is engaged b said clamping member and serves to distri ute the stresses received therefrom throughout a considerable portion of the abrasive se cut.

12. A grinding wheel comprising a rotatable drum, a plurality of abrasive segments mounted thereon, each segment having an under cut wedging surface of metal integral therewith, and a clamping device on the drum having a wedge portion engaging said wedgin surface and serving to draw the segment ad justably into position on the drum.

13. A grinding wheel comprising a revolu- 'ble drum, abrasive segments mounted on the periphery of the drum, means clamping against a surface of a segment to fasten it removably on the drum, and smooth facings integral with the segment shapedto fit against the drum and said clamping means to minimize breakage of the segment due to the pressure of clamping it on the drum.

14. A grinding wheel comprising a rotatable drum, a plurality of segments on the drum, each having an undercut wedging face of metal integral therewith and a metal surface fitting against the drum, and clamping devices on the drum fitting against said un-' dercut faces and arranged to clamp the segments tightly on the drum.

15. A grinding wheel comprising a rotatable support, a plurality of bonded abrasive segments mounted thereon to form an operatlve grinding surface, a shoe between each segment and the support which positions the segment correctly and transmits stresses therefrom to the support throughout an extensive area, means for adjustably clamping the segments in place, and a filler in the crevices between the segments which supports the segments laterally one against another, so as to form a rigid wheel structure.

16. A pulp grinding stone comprising a rotatable drum, a plurality of abrasive segments a....., clamping, blocks a; hold said segments removably. positioned on the drum, eachsegment having a metal facing which fits accurately against the drum and the clamping block and a metallic filler between he segments which will wear at substantially the same rate as the segments during a normal grinding operation. 17. A pulp grinding wheel comprising-a rotatable drum, a plurality of abrasive segments thereon, each segment having a metal facing which fits accurately against the drum surface, means to fasten the segments on said filled to the cylindrical surface of the wheel during the normal grinding operation. a

18. A grinding wheel comprising a rotatable support, a plurality of bonded abrasive segments mounted thereon to form an operative grinding surface, a metal shoe integral with the inner surface of each segment which fits accurately against the support, means for adjustably fastening the segments on the support, and a filler of a low melting, durable metal cast in the crevices between the segments which supports them laterally and is capable of wearing away as fast as the abrasive segments wear during a normal grinding operation. 19. As an article of manufacture, a. seg

ment of ceramic bonded abrasive rains having an outer convex grinding su ace, a concave surface opposed thereto and a groove providing a clamping shoulder, and a facing of material molded integrally on the concave surface which is shaped to fit against a supporting drum.

20. An abrasive segment comprising a body of bonded abrasive grains having a convex grinding surface and an undercut clamping portion provided with a metal facing integral therewith which is arranged to fit against a clamping wedge. 7

21. An abrasive segment comprising a. body of ceramic bonded abrasive grains having a grinding surface and a clamping shoulder, and a facing of durable material formed on said shoulder which has a smooth surface adapted to fit against a clamping device.

22. An abrasive segment comprising a body of ceramic bonded abrasive grains having an outer cylindrical grinding surface and a clamping portion, a metal facing integral with said portion for engaging a clamping device and a metal facing having a convex surface shaped to fit against a supporting drum.

23. An abrasive stone comprising segments of abrasive grains bonded by vitrified ceramic material which are arranged to form a grinding surface and which are spaced apart and. united into an integral body by means of metal flowed between such segments and into the surface pores thereof. 7 Y

24. An abrasive stone comprising segments of ceramic bonded [abrasive .grains which are shaped and arranged to form a cylindrical grinding surface, said segments having radial faces spa: apart, and a filler of a low melting metal flowed into the cre- .vices between said faces and into the surfac'epores thereof which unites the segments into an integral wheel structure.

25. A grinding wheel comprising a drum, a plurality of abrasive segments mounted on the drum to form a cylindrical grindin surface, means to fasten the segments rigi 1y on the drum, and a fillerof metal cast in place betwen the segments and. into the sur face pores thereof which holds the segments rigidly in position and forms an integral structure thereof, said so ents bein made of coarse abrasive grains onded by vitrified ceramic material. v 26., A grinding wheel comprising a rotatable support having a cylin rical surface, a plurality of bonded abrasive segments which have inner surfaces shaped to fit accurately against said cylindrical surface and clamping shoulders, and adjustable clamping devices mounted on the drum and fitting closely against said shoulders, which serve to fasten the segments rigidly against the cylindrical surface of the support.

27 A'grinding wheel comprising a revoluble drum, abrasive segments thereon which have beveled clamping shoulders and inner faces fitting accurately against the drum surface, wedge blocks adjustably fastened to the drum and clamping against'said shoulders to hold the segments rigidly in position on the drum, and a filler in the crevices between the segments.

28. A grinding wheel comprising a revo- ,luble drum, abrasive segments mounted on the periphery thereof to form a cylindrical grinding surface, each of which has a clamping shoulder provided with a smooth facj ing, clamping blocks fitting against said facings and means for adjustably fastening the blocks on the drum and thereby clamping cal surface, and adjustable clamping devices on the support, each engaging a portion of 'a segment opposed to the facing, which serve to maintain the contact facing in engagement with said cylindrical surface.

30. A grinding wheel comprising a. revolvable support for abrasive segments havin a cylindrical surface a plurality of abrasive segments carried y the sufifort and arranged toform'a substanti y continuous abrading surface, and clamping devices on the support engaging the segments and holding them against said cylindrical ,surface, each of said segments having smooth facings intimately united with and preformed on oppositely disposed portions thereof which enage said cylindrical surface and a clampmg device and afford contact faces corresponding to their contours. 31. A grinding wheel comprising a rotatable support having a cylindrical surface, a plurality of abrasive segments mounted on said surface and forming a cylindrical grinding surface, each segment having opposed clamping shoulders, clamping members associated with the support and said shoulders for adjustably and removably fastening the segments in .osition and a shoe of hard. durable material etween and fitting each clamping member and the associated shoulder of the segment. i

. Si ed at Worcester, Massachusetts, this 5th ay of August, 1924. WALLAGE W. GREENWOOD. 

